There are a number of ways to raise oil and gas from subterranean formations. Some wells initially have sufficient pressure that well fluids and/or gases flow to the surface and into tanks or pipelines without assistance. Some wells employ pumps and or compressors to bring the oil and/or gases to the surface and finally to the tanks or pipelines. However, even in wells with sufficient pressure initially, the pressure may decrease as the well gets older. When the pressure diminishes to a point where the remaining oil and/or gas is less valuable than the cost of getting it into the tanks or pipeline using secondary recovery methods, (production costs exceed profitability) the remaining oil and/or gas is not raised.
Compressors for this service are expensive, dangerous, require numerous safety devices, and still may pollute the environment. Reciprocating compressors are normally used to achieve the pressure range needed for “gas lifting” technology and pipeline transport. Existing reciprocating compressors are either directly driven by a power source, or indirectly driven via a hydraulic fluid. While both are suitable for compressing “lifting gas” or gas into a pipeline, most prior art reciprocating compressors are costly to operate and maintain. Moreover, existing reciprocating compressors are limited to compressing dry gases because they are not designed to pump both gas and liquids simultaneously and continuously. Prior art hydraulically driven compressors tolerate liquids and high compression ratios better than conventional direct mechanically driven reciprocating compressors, but are limited in how they can be installed and require interconnecting piping and cooling between stages.
Existing compressors use many different forms of speed and volume control. Direct drive and belt drive compressors use cylinder valve unloaders, clearance pockets, and rpm adjustments to control the volume of gas they pump. While these serve the purpose intended, they are expensive and use power inefficiently compared to the present invention. Some prior art compressors use a system of by-passing gas to the cylinders to reduce the volume compressed. This works, but it is inefficient compared to the present invention.
Another example of the inefficiency of prior art technology relates to current means for separating well products. Existing methods employ separators and scrubbers to separate primary components (liquids and gases) so that the gas can be compressed without damaging the compressor. In each case, controls, valves, and accessories add to the cost, environmental impact and maintenance of the equipment.